Why does my PDF NSImage print to paper at low res screen resolution? (was Re: how to get a sub piece of an NSImage or make a new NSImage that is a subset of an existing one)

FROM : Chad Leigh
DATE : Sat Aug 12 10:59:15 2006

On Aug 12, 2006, at 1:47 AM, Chad Leigh wrote:

>
> On Aug 12, 2006, at 12:01 AM, Chad Leigh wrote:
>

>>
>> On Aug 11, 2006, at 11:43 PM, Jonathan Grynspan wrote:
>>

>>> You can find more information on Cocoa's graphics model at http://
>>> developer.apple.com/documentation/Cocoa/Conceptual/
>>> CocoaDrawingGuide/index.html . Of particular interest to you may 
>>> be the sections on Graphics Contexts and Images.

>>
>> I am reading that now, thanks.
>>
>> Unfortunately my new image is a cached screen representation and 
>> not the hi-res PDF that it was before.  And it appears from the 
>> CocoaDrawingGuide docs under "Creating Graphics Contexts" that you 
>> cannot create a new PDF image using the code below.  It says :-
>> ( "Important:  You cannot create a viable graphics context for PDF 
>> or PostScript canvases using the graphicsContextWithAttributes: 
>> method. You must go through the Cocoa Printing system instead." 
>> That however, is what I need to do, I think.

>
> It looks like something like this works:
>
>          NSImageView *imageView = [[[NSImageView alloc] 
> initWithFrame:labelPDFRect] autorelease];
>          [imageView setImage:newLabel];
>          [imageView beginDocument];
>          NSMutableData    *imageData = [NSMutableData data];
>          NSPrintOperation *pdfOp = [NSPrintOperation 
> PDFOperationWithView:imageView insideRect:imageRect toData:imageData];
>          [pdfOp runOperation];
>          label = [[NSImage alloc] initWithData:imageData];
>     //     [pdfOp cleanUpOperation];
>          [imageView endDocument];
>
>
> I get my image and it is still a PDF based image by looking at the 
> single NSImageRep (NSPDFImageRep) that it contains, though I have 
> not yet gotten my printing code to spit out the image as I seem to 
> have screwed something up and all I get now is a gray box the size 
> of the page (without margins) so the paper comes out with a gray 
> box with normal white  margin.  This happens even when I use my PNG 
> image code so I screwed something up somewhere.


Ok, I fixed my screwed up print code -- I had a blank subview that 
had been added in one of my dead-end attempts at fixing this.

It appears that I am getting a PDF image from the above code. 
However, it is either a screen image quality representation or when I 
draw it to the printer view in my NSPrintOperation, it somehow gets 
converted to a screen resolution low res.

I capture the PDF to a file when I get it from the wire and I can 
print that and it is a "high resolution" image just like you would 
expect the PDF to be.

I have an alternate version of my code that uses PDFPage/PDFView etc 
with AffineTransforms to print to my page from just a portion of the 
PDF page.  So I know the original PDF is not a low res bitmap to start

Here is how I create the original NSIMage

    [finalImage appendBytes:(const void *)finalImageBytes length:k];
//    [finalImage writeToFile:@"express_label.pdf" atomically:YES];
    newLabel = [[NSImage alloc] initWithData:finalImage];

(gdb) po newLabel
NSImage 0x1607ba30 Size={612, 792} Reps=(
    NSPDFImageRep 0x1609ac40 Size={612, 792} 
ColorSpace=NSCalibratedRGBColorSpace BPS=0 Pixels=612x792 Alpha=NO
)
(gdb)

Question on the above -- is the Pixels here a real pixels size or is 
it like the page -- a coordinate system that does not really relate 
to actual pixels?  The way the image is drawn it appears to be a real 
pixel count -- how can I get the NSImage (NSPDFImageRep) to not 
degrade when I create it?

// (I now calculate some rects to grab the top half of the image and 
make a new image -- this part is snipped )

// create new image

        NSImageView *imageView = [[[NSImageView alloc] 
initWithFrame:labelPDFRect] autorelease];
        [imageView setImage:newLabel];
        [imageView beginDocument];
        NSMutableData    *imageData = [NSMutableData data];
        NSPrintOperation *pdfOp = [NSPrintOperation 
PDFOperationWithView:imageView insideRect:imageRect toData:imageData];
        [pdfOp runOperation];
        label = [[NSImage alloc] initWithData:imageData];
   //     [pdfOp cleanUpOperation];
        [imageView endDocument];

(gdb) po label
NSImage 0x1685f80 Size={612, 416} Reps=(
    NSPDFImageRep 0x16063a30 Size={612, 416} 
ColorSpace=NSCalibratedRGBColorSpace BPS=0 Pixels=612x416 Alpha=NO
)
(gdb)


       return [label autorelease];

// gets saved away

// later in print code

// calculate a new target rect based on the paper size from the 
NSPrintInfo -- not shown

// print to the print view -- show in gdb the label before it is drawn

(gdb) po label
NSImage 0x1685f80 Size={612, 416} Reps=(
    NSPDFImageRep 0x16063a30 Size={612, 416} 
ColorSpace=NSCalibratedRGBColorSpace BPS=0 Pixels=612x416 Alpha=NO
)
(gdb)

   [label drawInRect:labelRect fromRect:imageRect 
operation:NSCompositeCopy fraction:1.0];


// more drawing code for text etc

When this gets printed on paper the PDF is a low-res "screen" type 
image and not the crisp original PDF image

What have I done wrong?

Thanks
Chad


>
> Chad
>
>

>>
>> Thanks
>> Chad
>>

>>>
>>> -Jonathan Grynspan
>>>
>>> On 12-Aug-06, at 1:34 AM, Chad Leigh wrote:
>>>

>>>>
>>>> On Aug 11, 2006, at 11:28 PM, Jonathan Grynspan wrote:
>>>>

>>>>> Try the following:
>>>>>
>>>>> NSImage *partOfImage(NSImage *input, NSRect targetRect) {
>>>>>     if (input) {
>>>>>         NSImage *output = [[NSImage alloc] initWithSize: 
>>>>> targetRect.size];
>>>>>         [output lockFocus];
>>>>>         [input
>>>>>             drawAtPoint:    NSZeroPoint
>>>>>             fromRect:    targetRect
>>>>>             operation:    NSCompositeCopy
>>>>>             fraction:        1.0f];
>>>>>         [output unlockFocus];
>>>>>         return [output autorelease];
>>>>>     } else {
>>>>>         return nil;
>>>>>     }
>>>>> }

>>>>
>>>> Thanks, I will.  I've been reading the lockFocus and the 
>>>> drawAtPoint stuff since I posted the first request, trying to 
>>>> put my brain around it.  This helps immensely!
>>>>
>>>> Thanks
>>>> Chad
>>>>

>>>>>
>>>>> -Jonathan Grynspan
>>>>>
>>>>> On 12-Aug-06, at 1:17 AM, Chad Leigh wrote:
>>>>>

>>>>>> I have a Cocoa app and I get a PDF image over the internet 
>>>>>> that I store in an NSImage using
>>>>>>
>>>>>>    label = [[NSImage alloc] initWithData:finalImage];
>>>>>>
>>>>>>
>>>>>> The image previously was a PNG image and was exactly the image 
>>>>>> needed.  Now that they pass a PDF image, they pass an image 
>>>>>> that is an image of a complete piece of paper with the image I 
>>>>>> am interested in placed on the upper half of this virtual 
>>>>>> paper (the rest is just blank).  The image is always in the 
>>>>>> same place and the same size so I can determine a Rect that 
>>>>>> will always work to select it.  I want to extract this image 
>>>>>> out of the PDF and create a new NSImage (or overwrite the old 
>>>>>> one, I don't care) that I can use later on to print in my own 
>>>>>> existing print routine and to display thumbnails of it.
>>>>>>
>>>>>> I do not see how to go about it.  Most of the draw/composite 
>>>>>> routines I see in NSImage rely on an existing userspace to 
>>>>>> draw into.  I want to "draw" into a new NSImage.  My brain is 
>>>>>> having a hard time adjusting to think about how to do this.
>>>>>>
>>>>>> Ideally I want something like
>>>>>>
>>>>>>     NSImage *newImage = [[NSImage alloc] initFromImage:oldImage 
>>>>>> usingRect:targetRect];
>>>>>>
>>>>>> I expect what I want to do is very easy but if someone could 
>>>>>> point me on the way I should be exploring I would appreciate it.
>>>>>>
>>>>>>
>>>>>> Thanks
>>>>>> Chad
>>>>>>
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>>>>>
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>>>>
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